1. Field of the Invention
The present invention relates to a system for projecting an image on a projection surface in a dome (to be referred to as a dome surface hereinafter).
In this specification, three terms, i.e., an "original", an "image", and a "projected image" are used. These terms are defined as follows.
1. Original . . . indicates a medium on which an image is displayed. As typical originals, optical original plates such as projection films and reversal films are known. For example, the original plates also include an active image display device such as a CRT or an LCD. In this invention, the latter rather than the former is supposed as a main original. PA0 2. Image . . . indicates an image displayed on an original. The image is displayed on an optical original plate such as a projection film or a reversal film. In an active image display device, an image is displayed on an image surface (projection surface). Generally, an "original" and an "image" need not be discriminated from each other. However, this invention has a characteristic feature that an original itself is not deformed, but an image displayed by the original is displayed to obtain a secondary image. For this reason, both the original and the image are not discriminated from each other. PA0 3. Projected image . . . indicates an image projected on a projection surface when an image is projected by a projection optical system. PA0 1. The waveforms of horizontal and vertical scanning voltages of a video projector are adjusted, so that an image to be projected is deformed (Japanese Patent Application Laid-Open No. 9-149351). PA0 2. The positions of pixels of a video projector are adjusted, so that an image to be projected is deformed (Japanese Patent Application Laid-Open No. 8-88822).
2. Description of Related Art
A facility in which an image is projected on a spherical dome surface in place of a flat screen is well known as a global full-arc movie theater.
If an angle of view obtained when a video image is photographed is equal to an angle of projected view of a projector, as far as an audience watch a video image from the same point as that of a projection position, the same correct video image as that obtained in photographing is reproduced for the audience. However, the projection position cannot be theoretically made equal to the audience position. In addition, identical lenses are not used as a photographing lens and a projection, and the angles of projection view of both the lenses are not equal to each other. For this reason, in such a case, if a video image is observed from a projection position or a photographing position, a correct video image is not reproduced.
The above conditions are also satisfied on a dome surface. In this case, when the installation position of a projector is set at the center of the dome, a video image the smallest distortion can be watched by all the audience. However, in fact, the projector can be installed at such a position due to the arrangement of audience seats or the installation environment of the projection. As a result, the projector is actually installed at a position being out of the center of the dome.
When the projector is installed at the position being out of the center of the dome, the actual shape of an object is not similar to the projected image, and the projected video image is distorted. For this reason, an angle of projected image is made narrow to project a video image whose distortion is not conspicuous, or a large video image is directly projected without regarding distortion itself. However, the feeling of being at a live performance which the video image originally has cannot be reproduced because of a narrow angle of view in the former and because of distortion in the latter.
In addition, it is supposed that one video image is divided by a plurality of projectors to be projected on a dome surface. In this case, installation of the projectors at ideal positions means concentric installation of the projectors at the center of the dome, and realization of the installation is not real.
In order solve the problem described above, the present applicant invented a projection method in which, when an image is projected from at a position other than the center of a dome onto a predetermined projection surface, a projected image having small distortion obtained when the same image is projected from the center of the dome onto the same projection surface is supposed, the image to be projected is deformed such that the projected image projected by a projector installed at a position other than the center of the dome, and distortion of the projected image projected on the dome surface is removed as a result. This method was disclosed in Japanese Patent Application Laid-Open Nos. 8-88822 and 9-149351. The present invention relates to a means for deforming an image to performing the invention described above.
In order to obtain a projected image having small distortion, with respect to means for deforming an image to be projected, the following two means are disclosed in the known references described above.
However, the means corresponding to the former must superpose waveforms given by a complex function for a vertical/horizontal polarizing circuit. In addition, the means can be applied to only a projector such as a CRT having a form in which scanning is performed by an electronic beam. The means could not be applied to a solid-state display device such as an LCD which have been mainly used in recent years.
On the other hand, the means corresponding to the latter can be applied to a solid-state display device such as an LCD. However, a dedicated device in which the pixel arrangement/pixel size of the display device itself is change must be manufactured, or a large-scale circuit for performing rearrangement of pixels for deformation must be added.
In addition, as a matter of course, any one of the means can be applied to only a projector such as a projector, i.e., an LCD or a CRT in which an image is displayed on a video image surface by an electric signal to project the image on a projection surface through an optical system.